Drying Practical correct PDF

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ABSTRACT The usefulness of drying operation cannot be overemphasis in the production industries because most industries employed the use of this process on their product. Most industries which specialize on food production, pharmaceuticals, wood and timber processing and agriculture seamlessly use drying operation on their products. Therefore, the study of drying operation is inevitable for a chemical engineering student. As a result, the drying process in this experiment is being investigated. As a case study or a sample, clay was used. The aim of the experiment was to determine the rate at which the clay sample dried, as well as the moisture content, moisture loss, and the effect of the container's surface area on the rate of drying. During the experiment, the wet clay was placed in an oven that had already been preheated to 105°C and was removed at 4-minute intervals for weighing to determine the moisture loss. The experiment will continue until the sample's moisture content is as low as possible. At the conclusion of the experiment, it was discovered that the drying rate increased dramatically at the start of the experiment, then remained steady for a short period before dropping dramatically.

CHAPTER 1

1.1

INTRODUCTION

The vaporization of liquid occurs when heat is applied to wet feedstock, granules, filter cakes, and other materials. Since virtually any plant and facility that manufactures or handles solid materials, in the form of powder and granules, drying solid materials is one of the most common and critical unit operations in the chemical process industries (CPI). Materials drying is often the last step in the manufacturing process, completed just before packing or dispatch. Evaporation, filtration, and crystallization are often followed by drying, which is the final removal of water or another solute. While, in the majority of processing industries, drying is carried out for one or more of the following purposes, drying is an integral part of the manufacturing process in certain cases, such as in paper making or timber seasoning. Drying a crystalline substance, it's critical that the crystals don't get destroyed, and pharmaceutical products must be handled with caution to prevent contamination. Shrinkage, like with paper, splitting, like with wood, and flavor loss, like with fruit, must all be avoided. Almost all drying methods involve the removal of water by vaporization, which involves the addition of heat, with the exception of partial drying of a substance by pressing in a press or the removal of water by adsorption. The successful utilization of the heat supplied is the most important factor when evaluating the performance of a drying process. The drying process was performed on a clay soil sample. To evaluate the effect of shape on drying time, the experiment was conducted using two different containers with different shapes: cylindrical and spherical containers. The rate of drying and moisture content of the given clay sample were determined at the end of the experiment with respect to the various formed containers. 1.2

AIM OF EXPERIMENT

The drying experiment is carried on the clay sample for: 1. Determination of the rate of drying 2. Determination of the critical moisture content. 3. The effect of shape of container on the drying rate.

1.3

LIMITATIONS OF EXPERIMENT

The following were the limitations encountered during the course of experiment which tends to reduce the quality of the result. 1. During the course of the experiment, there were power outages. This was a lot of stress because we have to wait for the drying setup to be heated back to the desired temperature. This takes more time and tarred the quality of the experiment done.

1.4

SIGNIFICANCE OF EXPERIMENT Drying operations are of vital roles in the industries and different sectors such as:

1. Food Foods are dried to prevent microbial growth and quality degradation. The amount of drying, on the other hand, is determined by the product's intended use. After harvest, cereals and oilseeds are dried to a moisture content that allows for microbial stability during storage. Blanching vegetables before drying prevents rapid darkening, and drying is done not only to prevent microbial growth but also to prevent browning during storage. 2. Processing of Wood and Timber The processing of wood for the manufacture of paper, flax, and washing powder necessitates careful drying. 3.Fecal Sludge Treatment and Sewage Treatment Drying sewage sludge from sewage treatment plants, fecal sludge, or feces collected in urine diverting dry toilets (UDDT) is a popular method for pathogen kill in the sanitation sector, as pathogens can only withstand a certain degree of dryness. 2. Agriculture is one of the most important industries in For a wide range of farmers across a variety of crops, drying is also a vital part of harvest and post-harvest operations. The drying process is also used in seed production and is an important part of a seed's quality and possible longevity. Application in the Pharmaceutical Industry

To prepare granules for tablets and capsules, dried aluminum hydroxide, lactose, and powder extracts, and to minimize bulk density and weight, a drying operation is used. Reuse of Catalyst At the end of the experiment, the moisture is drained from the catalyst so that it can be reused.

CHAPTER 2 2.0

THEORETICAL PRINCIPLE

Drying is a mass transfer process that involves evaporation from a solid, semisolid, or liquid to remove water moisture or moisture from another solvent (hereafter product). The final product must be solid, such as paper, sand, wood, salts, and so on, in order to be considered "dried." There must be a source of heat and a sink for the vapor emitted in order to accomplish this. Drying is the process of removing a small amount of water from a substance in order to minimize its liquid content to a level that is appropriate. It's the last operation before the packaging point. The drying process may be batch or continuous.

2.1

RATE OF DRYING

Heat trThe rate of drying is the time it takes for a solid to dry under the same conditions for which a drying curve has been fully determined; the difference in the corresponding time to the original and final moisture contents must be read from the curve. The drying rate can be measured for such a curve. In drying processes, mass and heat transfer are important. Heat is applied to the substance, causing the liquid to evaporate, and mass is transferred to the surrounding gas as a vapor. The collection of factors that influence heat and mass transfer decide the drying rate. The constant-rate cycle and the falling-rate period are two distinct drying zones that solids are thought to observe. A break point known as the essential moisture content separates the two regions.

2.2

CONSTANT RATE PERIOD

Section AB reflects the constant-rate duration in a standard graph of moisture content versus drying rate and moisture content versus time (Figure 1). Moisture is thought to evaporate from a saturated surface at a rate regulated by diffusion from the surface through the stationary air film in contact with it in that region. This time is determined by the air temperature, humidity, and moisture transport speed to the surface, all of which influence the temperature of the saturated surface. Water must be delivered to the surface at a constant rate to sustain saturation over the constant rate phase. Figure 1. Segment AB of the graph represents the constant-rate drying period, while segment BC is the falling-rate period A break in the drying curve occurs near the end of the constant rate cycle (point B, Figure 1).

The critical moisture content is reached at this stage, and subsequent drying results in a linear decrease in the drying rate. The first falling-rate cycle occurs in this portion, segment BC. Moisture reaches the surface at a slower rate as drying progresses, and the process that governs moisture transfer has an impact on drying speed. The surface would begin to rise above the wet bulb temperature because it is no longer saturated.

The second falling-rate duration, which is defined by segment CD in Figure 1, is regulated by vapor diffusion. Diffusion can occur as a result of the concentration gradient produced by the loss of water at the surface. Evaporation, capillary forces, or a period of vaporization and condensation, as well as osmotic effects, may all contribute to the gradient. 2.3

FIRST FALLING PERIOD This denotes a situation where the surface can no longer provide enough free moisture to saturate the air in contact with it. The rate of drying under these conditions is highly dependent on the process by which moisture from inside the material is transferred to the surface. 2.4

SECOND FALLING PERIOD It is reasonable to conclude that the surface is dry and that the plane of separation has passed into the solid at the end of the first dropping rate cycle. In this case, evaporation occurs inside the solid, and the vapor is transported to the surface through molecular diffusion. The forces that govern vapor diffusion decide the final rate of drying, and they are completely independent of external conditions.

2.5

DRYING ENDPOINT There are many methods for determining when the drying process is complete. The most popular method is to create a drying curve by taking samples at various stages of the drying cycle and comparing them to the drying period. When the drying is finished, the product temperature will begin to rise, signaling that the drying has reached the desired moisture content. In batch processes, Karl Fischer titration and loss on drying (LOD) moisture analyzers are also commonly used. A gravimetric moisture-sorption apparatus with vacuum-drying capability is used to test the water vapor sorption isotherms. Electrical-resistance-type meters are used to measure moisture content in grain, wood, food, textiles, pulp, paper, chemicals, mortar, soil, coffee, jute, tobacco, rice, and concrete. This type of instrument works on the basis of electrical resistance, which varies slightly depending on the moisture content of the object being measured. Moisture meters that are dielectric are also used. They use a flat plate electrode that does not penetrate the substance to make surface contact.

2.6

TYPES OF DRYER 1. The solids are dried by direct contact with gases, normally forced air, in adiabatic dryers. Moisture is on the surface of the solid in these dryers. 2. Non-adiabatic dryers are those that don't use heated air or other gases to provide the energy needed to complete the drying process. 3. The following processes of heat transfer can also be used to classify dryers: 4. Explicit (convection) 5. Communication or indirect (conduction) 6. Luminous (radiation) 7. Microwave (radio frequency) or dielectric drying

DIRECT OR ADIABATIC DRYERS:They provide the heat of vaporization of the liquid by using the sensible heat of the fluid that touches the solid. Solid materials may be exposed to heated gases in adiabatic dryers in a variety of ways, including the following: • Gases may be blown over a surface (cross circulation); used while solids are stationary, such as wood, corn, and others. • Gases may be blown through a bed of solids to fluidize the particles, similar to how solids are lowered slowly through a slow-moving gas stream in a rotary dryer

. • Solids can penetrate a high-velocity hot gas stream and be transported pneumatically to a collector (flash dryer) in this case, much as in a fluidized-bed dryer. NON-ADIABATIC DRYERS (contact dryers): involve an indirect method of removal of a liquid phase from the solid material through the application of heat, such that the heat-transfer medium is separated from the product to be dried by a metal wall. Heat transfer to the product is predominantly by conduction through the metal wall and the impeller. Therefore, these units are also called conductive dryers.

CHAPTER 3 3.1

DESCRIPTION OF APPARATUS The following apparatus were used during the course of the drying experiment. 1. LABORATORY OVEN Oven was utilized to carry out the drying process on the sample. It was set at temperature controlled by a thermistor.

Figure 3.1: Oven

2. SIEVE Sieve apparatus was used to separate the clay sample size. The fraction of the clay to be used was gotten.

Fig 3.2 Sieve 3. CLAY SAMPLE The sample given for the drying experiment was a clay.

Fig 3.3 Clay Sample.

4. CONTAINER Two different container were used during the experiment. These container has different shapes to ascertain the effects of the surface area of this container on the rate of drying of the sample. 1. Spherical Container

Figure 3.4 Spherical Container 2. Cylindrical Container

Figure 3.5 Cylindrical Container

5. STOPCLOCK Stopcock was engage to get the intervals of putting the sample out of the oven for weighing.

Fig 3.6: Stopclock. 6. WEIGHING BALANCE Weighing balance was engaged to measure the sample weight, water and consecutively measuring of dried sample.

Fig 3.7 Weighing Balance

3.2

EXPERIMENTAL PROCEDURES RECOMMENDATION 1. Séverine, Thérèse, Mortier, F.C., De Beer, Thomas, Gernaey, Krist V., Vercruysse, Jurgen, et al. “Mechanistic modelling of the drying behavior of single pharmaceutical granules,” European Journal of Pharmaceutics and Biopharmaceutics. 80, pp. 682–689, 2012. 2. Coulson Richardson’s chemical Engineering Vol 2, page 900 – 910. 3. Mezhericher, M., Levy, A. and Borde, I., “Theoretical drying model of single droplets containing insoluble or dissolved solids,” Dry. Technol. 25 (6), pp. 1025– 1032, 2007....